One aspect of this invention is an environmentally friendly, low phytotoxic acidic aqueous pesticide composition and a method for killing a soft-bodied animal (e.g. a Coqui frog; a Coqui frog egg; a tree frog, a cane toad, a slug, a nettle, a caterpillar, a nematode, an aphid, a spider mite, fruit fly larva, a varro mite and other soft bodied insects that are usually regarded as pests, or a combination thereof). More specifically, the acidic aqueous pesticide composition comprises: a low concentration of organic acid solution (less than 25%) and having a low pH (below about pH3). The active ingredient in the pesticide composition can be selected from acidic calcium sulfate (ACS), propionic acid, citric acid, or various functional equivalents including salts and esters, as described herein. The acidic aqueous pesticide composition of can further be formulated to comprise a sulfuric acid solution having a concentration below 10% (w/v) as a percentage of the aqueous pesticide composition. Additionally, the aqueous pesticide composition may further comprise a surfactant for the surface area of the aqueous pesticide composition on the soft bodied animal of interest wherein the surfactant is selected from: an ionic-, anionic-, zwitterionic-surfactant, or combination thereof.
Another aspect of the current invention is a method of killing a soft-bodied animal of interest with an acidic pesticide composition, the method comprising the steps of: locating the soft-bodied animal or locating an area where the soft-bodied animal resides; contacting the soft-bodied animal with one of the acidic pesticide compositions described herein. About 1 ml of this composition coming in contact with Coqui Frogs is lethal in less than about 15 minutes. This acidic pesticide composition represents a low environmental impact pesticide made from all GRAS ingredients also used in food processing and which are low in phytotoxicity.
The Coqui Frog: Hawaii's lush vegetation, warm temperatures and high humidity not only welcome human visitors but also indiscriminately provide a tropical paradise for the over 1,000 non-native plants, vertebrates, and invertebrates that have been accidentally introduced over the past 65 years. Some non-native species have become established at the expense of native species, competing for habitat and nutrient sources.
The Coqui frog, Eleutherodactylus coqui, was accidentally introduced into Hawaii from Puerto Rico in about 1988. Aside from being a major noise nuisance, the frogs pose a threat to Hawaii's island ecosystem. Coqui frogs have a voracious appetite that puts Hawaii's unique insects and spiders at risk directly. These frogs also compete with endemic birds and other native fauna that rely on insects for food. The frogs are quite adaptable to the different ecological zones and elevations in the state, which is demonstrated by populations being found from sea level to 4,000 feet elevations. Scientists are also concerned that an established coqui frog population may serve as a readily available food source if (or when) brown tree snakes are accidentally introduced in Hawaii.
Coqui frogs belong to a genus of frogs that do not have a tadpole stage and therefore do not require a body of water to reproduce. Instead, the female lays the eggs on damp moss or leaf litter, or inside a rolled or folded leaf, and the eggs are brooded by the male, who keeps them moist until they hatch.
At first, the eggs look white to off-white and opaque, about the size of large tapioca pearls. As they mature, the eggs enlarge, darken and become transparent, resembling papaya seeds, with the frog embryo visible inside. When the tiny froglets hatch in 14-17 days, they are about 5 mm long.
In its native Puerto Rico, the female coqui frog usually lays a cluster or clutch of 34-75 eggs four to six times a year. Under laboratory conditions in Hawaii, mating pairs can produce a clutch every 2½ weeks without loss of fertility, which results in about 26 clutches per year, or more than 1,400 eggs per female per year. It takes about 8 months for froglets to mature, and adult coqui frogs may live as long as 4-6 years.
Coqui populations have exploded in Hawaii over the last 15 years from presumably a single infestation to over 200 infestations on the Big Island alone. These frogs are also present on Maui (e.g. 40 or more infestations), Oahu (5 sites) and most recently on Kaua'i (1 site, which was the subject of an eradication effort with citric acid). In their native Puerto Rico, a 20×20 m plot averages about 40 reproductively mature adults (note: this number excludes juveniles). In contrast, a 20×20 m plot on the big island contains >200 reproductively mature adults. One reason for the population explosion is believed to be the lack of natural predators (e.g. owls, snakes, tarantulas, scorpions) in Hawaii.
Respiration and Circulation in Frog Skin. Although not wanting to be bound by theory, many of the methods described below take advantage of the skin of a frog being permeable to oxygen and carbon dioxide, as well as to water. Briefly, there are a number of blood vessels near the surface of the skin. When a frog is underwater, oxygen is transmitted through the skin directly into the bloodstream. On land, adult frogs can use their lungs to breathe, but the chest muscles are not involved in respiration, and there are no ribs or diaphragm to support breathing. Frogs breathe by taking air in through the nostrils (which often have valves which close when the frog is submerged), causing the throat to puff out, then compressing the floor of the mouth, which forces the air into the lungs. In August 2007 an aquatic frog named Barbourula kalimantanensis was discovered in a remote part of Indonesia. The Bornean Flat-headed Frog (B. kalimantanensis) is the first species of frog known to science without lungs.
Frogs are known for their three-chambered heart, which they share with all tetrapods except birds, crocodilians and mammals. In the three-chambered heart, oxygenated blood from the lungs and de-oxygenated blood from the respiring tissues enter by separate atria, and are directed via a spiral valve to the appropriate vessel—aorta for oxygenated blood and pulmonary artery for deoxygenated blood. This special structure is believed to be essential to keeping the mixing of the two types of blood to a minimum, which enables frogs to have higher metabolic rates, and to be more active than otherwise.
Some species of frog have remarkable adaptations that allow them to survive in oxygen deficient water. The lake titicaca frog (Telmatobius culeus) is one such species and to survive in the poorly oxygenated waters of Lake Titicaca it has incredibly wrinkly skin that increases its surface area of the skin to enhance gas exchange. This frog will also do ‘push-ups’ on the lakebed to increase the flow of water around its body.
The Coqui frog has demonstrated its ability to quickly adapt to Hawaii's ecosystem by an unprecedented population explosion that can reach eight to ten thousand frogs per square acre. Such a mega-group of frogs is estimated to eat about 47,500 insects per night. The absence of natural predators and its noisy mating behavior have made the Coqui frog the target of government and community eradication efforts. There are many different methods currently used to control and eradicate the Coqui frog in Hawaii. Many of the eradication methods take advantage of the frogs ability to breath through its skin. Some methods are described below, however, one of ordinary skill in the art will realize that the methods of population control and/or eradication described herein are by no means all-inclusive.